The mechanism that lead to tolerization of autoreactive T cells to restricted peripheral antigens, such as islets antigens, have not been well defined. In addition autoreactive T cells that escape from negative selection and cause autoimmune diabetes have also not been well elucidated. Autoimmune regular (AIRE) is a newly discovered transcription factor regulating peripherally restricted antigens in thymic medulla epithelial cells (mTECs), that might control the deletion of the autoreactive T cells. Lack of AIRE in patients, or in mice leads to increased incidences of endocrine organ-specific autoimmunity. On the other hand, the lack of lymphotoxin (LT) causes wider lymphocyte infiltration into multiple organs. Our preliminary data showed that the LT beta receptor signaling pathway, possibly through NF-kB subunits, was necessary for the expression of self antigens in AIRE-dependent and independent pathway. We hypothesize that LT controls the expression of autoantigens in both an AIRE-dependent and -independent pathways leading to negative selection of autoreactive T cells. Furthermore, coordination of T cells escaping negative selection leads to persistent local inflammation, which is required for tissue-specific autoimmune destruction. 1) Using antibodies and soluble receptors to stimulating or inhibiting the LTBR pathway as well as using LTBR and AIRE KO mice, we will define AIRE-dependent and independent pathways involved in negative selection. We will define which NF-kB pathways, namely p52/RelB, p50/RelB, p52/RelA, or p50/RelA, is essential for LT-mediated AIRE induction of insulin; 2) We will address the role of local inflammation, increased apoptosis, and costimulation, in recruiting and activating these escaped autoreactive T cells inside islets causing autoimmune diabetes. The goal of this project is to define how autoreactive T cells are controlled by the stromal cells within the thymic and peripheral tissues and how cross-talk between autoreactive T cells against peripheral antigens and stromal cells dictates the development of autoimmune diabetes.